As shown in FIG. 11, generally, a cartridge-type syringe suited for disposable purposes comprises a cylindrical holder 101 which has at its distal end a mounting portion 102, constituted by a lock adapter to which a needle proximal portion 114 of an injection needle 113 is adapted to be connected, and a flange 103 at its proximal end, a discharge needle 105 fixedly fitted liquid-tight in a through hole 104, formed through a central portion of the mounting portion 102, with a pointed end thereof extended into the interior of the holder 101, a cartridge 110 which comprises a cylindrical tubular body 108 closed at its open distal end by a closure member 106 of rubber, and a piston 107 fitted liquid-tight into this tubular body to a predetermined position from an open proximal end thereof, and a predetermined amount of liquid medicine or the like sealed in the tubular body, and a piston rod 111 to be connected to the piston 107. A flange of a cap 109 fixedly holding the closure member 106 is disposed between front and rear projections 112 formed on the inner peripheral surface of the holder 101, so that the cartridge 110 fitted in the holder 101 is provisionally held in a position where the closure member 106 is spaced apart from the discharge needle 105 (Japanese Laid-Open Utility Model Application No. 2-55958).
In order to avoid a disadvantage that the piston rod 111 is inadvertently pushed to inject the liquid medicine or the like, for example, during transport, the piston rod 111 is separate, and after the tubular body 108 is pushed to cause the discharge needle 105 to pierce it, the piston rod 111 is intended to be connected to the piston 107 so as to effect the injection to the object. However, there is a fixed conception that the piston rod in the syringe is to be pushed, and therefore in most cases, the piston rod 111 is first connected to the piston 107, and the needle proximal portion 114 is connected to the mounting portion 102 to attach the injection needle 113 to the holder 101, and then the piston rod 111 is pushed to advance the tubular body 108 together with it to release the provisional holding condition achieved by the projections 112, to cause the discharge needle 105 to pierce the closure member 106, and the piston rod 111 is further pushed to advance tile piston 107 within the tubular body 108, thereby injecting the medicine or the like into the object via the discharge needle 105 and the injection needle 113.
Namely, in this conventional syringe, when the piston rod 111 is pushed, the tubular body 108 is advanced together with it since the liquid medicine or the like is sealed in a liquid tight manner, and it is necessary to apply a considerable force to the piston rod 111 in order to cope with a resistance offered when the discharge needle 105 pierces the closure member 106, and therefore the liquid medicine or the like is in a pressurized condition. Therefore, when the discharge needle 105 completely pierces the closure member 106, the liquid medicine or the like is discharged through the discharge needle 105, and in addition the liquid may leak from a gap between the closure member 106 and the discharge needle 105. And besides, when the complete piercing is achieved, the resistance is abruptly reduced, and the tubular body 108 is abutted against the distal end of the holder 101, and is stopped, and therefore the piston rod 111 may be pushed greatly, so that the liquid medicine is discharged in error in a large amount, which invites a disadvantage that the amount of injection into the object is greatly reduced.
Moreover, it is inconvenient to connect the piston rod 111 to the piston each time it is used.
Further, the reduced amount of injection into the object, which is caused by the wasteful discharge of the liquid medicine or the like, lowers the effect accordingly.
In the conventional cartridge-type syringe comprising the tubular holder having the injection needle-mounting portion at its distal end, the discharge needle fixedly mounted on the mounting portion with its pointed end extended into the holder, and the cartridge which comprises the tubular body of a predetermined length, the closure member mounted on the open distal end and pierceable by the discharge needle, the piston inserted to the predetermined position from the open proximal end, and the liquid medicine or the like sealed by these parts, wherein the cartridge is fitted in the holder so as to move back and forth, and is held in the position where the closure member is spaced apart from the discharge needle, the piercing of the discharge needle through the closure member by the pushing of the piston rod and the discharge of the liquid medicine or the like are effected in a continuous single operation, and therefore the liquid medicine or the like is liable to be discharged in error in a large amount, so that the amount of injection into the object is reduced, and besides since the piston rod is separate from the piston, they must be connected together each time they are used, and this is inconvenient. The problems to be solved by the present invention are these points.